Inconel Alloy 718 Ring UNS N07718/W.Nr. 2.4668 ASTM B637 Ring
Overview
INCONEL alloy 718 (UNS N07718/W.Nr. 2.4668) is a high-strength, corrosion-resistant nickel chromium material used at -423° to 1300°F.
The age-hardenable alloy can be readily fabricated, even into complex parts. Its welding characteristics, especially its resistance to postweld cracking, are outstanding.
The ease and economy with which INCONEL alloy 718 can be fabricated, combined with good tensile, fatigue, creep, and rupture strength, have resulted in its use in a wide range of applications. Examples of these are components for liquid fueled rockets, rings, casings and various formed sheet metal parts for aircraft and land-based gas turbine engines, and cryogenic tankage. It is also used for fasteners and instrumentation parts.
Limiting Chemical Composition, %
Nickel (plus Cobalt)............................................................................................................................................................50.00-55.00
Chromium............................................................................................................................................................................17.00-21.00
Iron.............................................................................................................................................................................................Balance.
Niobium (plus Tantalum)........................................................................................................................................................4.75-5.50
Molybdenum............................................................................................................................................................................2.80-3.30
Titanium...................................................................................................................................................................................0.65-1.15
Aluminum.................................................................................................................................................................................0.20-0.80
Cobalt.......................................................................................................................................................................................1.00 max.
Carbon......................................................................................................................................................................................0.08 max.
Manganese .............................................................................................................................................................................0.35 max.
Silicon.......................................................................................................................................................................................0.35 max.
Phosphorus............................................................................................................................................................................0.015 max.
Sulfur.......................................................................................................................................................................................0.015 max.
Boron.......................................................................................................................................................................................0.006 max.
Copper.......................................................................................................................................................................................0.30 max.
*Reference to the ‘balance’ of a composition does not guarantee this is exclusively of the element mentioned but that it predominates and others are present only in minimal quantities.
Physical Constants
Density |
lb/in^3(Annealed)............................................................................0.296 |
lb/in^3(Annealed and aged)............................................................0.297 | |
g/cm^3...............................................................................................8.24 | |
Specific Heat at 70°F |
Btu/lb °F (at 21°C, J/kg °C)...................................................0.104 (435) |
Melting Range |
°F..............................................................................................2300-2437 |
°C..............................................................................................1260-1336 | |
Curie Temperature,°F (°C) |
Annealed Material……...…................................................…...<-320(<-196) |
Annealed and Aged Material...….................................…..........-196(-112) | |
Permeability at 200 oersted and 70°F |
Annealed Material.........................................................................1.0013 |
Annealed and Aged Material........................................................1.0011 |
Mechanical properties
For most applications, INCONEL alloy 718 is specified as: solution annealed and precipitation hardened (precipitation hardening, age hardening, and precipitation heat treatment are synonymous terms). Alloy 718 is hardened by the precipitation of secondary phases (e.g. gamma prime and gamma double-prime) into the metal matrix. The precipitation of these nickel(aluminum, titanium, niobium) phases is induced by heat treating in the temperature range of 1100 to 1500°F. For this metallurgical reaction to properly take place, the aging constituents (aluminum, titanium, niobium) must be in solution (dissolved in the matrix); if they are precipitated as some other phase or are combined in some other form, they will not precipitate correctly and the full strength of the alloy with not be realized. To perform this function, the material must first be solution heat treated (solution annealed is a synonymous term).
Heat Treating
Two heat treatments are generally utilized for INCONEL alloy 718:
•Solution anneal at 1700-1850°F followed by rapid cooling, usually in water, plus precipitation hardening at 1325°F for 8 hours, furnace cool to 1150°F, hold at 1150°F for a total aging time of 18 hours, followed by air cooling.
•Solution anneal at 1900-1950°F followed by rapid cooling, usually in water, plus precipitation hardening at 1400°F for 10
hours, furnace cool to 1200°F, hold at 1200°F for a total aging time of 20 hours, followed by air cooling.
If the material is to be machined, formed, or welded, it typically is purchased in the mill annealed or stress relieved condition. The material is then fabricated in its most malleable condition. After fabrication, it can be heat treated as required per the applicable specification.
Tensile-properties
Typical mechanical properties |
Tensile strength Rm N/mm2 |
Yield Strength RP0.2 N/mm2 |
Elongation A5% |
Brinell strength HB |
Solution treatment |
965 |
550 |
30 |
≤363 |
Corrosion Resistance
INCONEL alloy 718 has excellent corrosion resistance to many media. This resistance, which is similar to that of other nickel-chromium alloys, is a function of its composition. Nickel contributes to corrosion resistance in many inorganic and organic, other than strongly oxidizing, compounds throughout wide ranges of acidity and alkalinity.
It also is useful in combating chloride-ion stress-corrosion cracking. Chromium imparts an ability to withstand attack by oxidizing media and sulfur compounds. Molybdenum is known to contribute to resistance to pitting in many media.
Available Forms
We provide you with a variety of product forms, including but not limited to
● Bar & Rod
● Pipe & Tube
● Coil & Strip
● Plate & Sheet & Circle
● Wire & Welding
● Fitting (Flange, Elbow, Tee...)
● Customize
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